The unraveling of the al Assad regime in Syria will produce many geopolitical consequences. One potential consequence has garnered a great deal of media attention in recent days: the possibility of the regime losing control of its chemical weapons stockpile. In an interview aired July 30 on CNN, U.S. Secretary of Defense Leon Panetta said it would be a "disaster to have those chemical weapons fall into the wrong hands -- hands of Hezbollah or other extremists in that area."

When he mentioned other extremists, Panetta was referring to local and transnational jihadists, such as members of the group Jabhat al-Nusra, which has been fighting with other opposition forces against the Syrian regime. He was also referring to the many Palestinian militant groups such as Hamas and the Popular Front for the Liberation of Palestine-General Command, which have long had a presence in Syria and until recently have been supported by the al Assad regime.

The fear is that the jihadists will obtain chemical weapons to use in terrorist attacks against the West. Israel is also concerned that Palestinian groups could use them in terrorist attacks inside Israel or that Hezbollah could use such weapons against the Israelis in a conventional military battle. However, while the security of these weapons is a legitimate concern, it is important to recognize that there are a number of technical and practical considerations that will limit the impact of these weapons even if a militant group were able to obtain them.

Militant Use of Chemical Weapons

Militant groups have long had a fascination with chemical weapons. One of the largest non-state chemical and biological weapons programs in history belonged to the Aum Shinrikyo organization in Japan. The group had large production facilities located in an industrial park that it used to produce thousands of gallons of ineffective biological agents. After the failure of its biological program, it shifted its focus to chemical weapons production and conducted a number of attacks using chemical agents such as hydrogen cyanide gas, phosgene and VX and sarin nerve agents.

Jihadists have also demonstrated an interest in chemical weapons. The investigation of the 1993 World Trade Center bombing found that bombmaker Abdul Basit (aka Ramzi Yousef) had added sodium cyanide to the large vehicle-borne improvised explosive device detonated in the Trade Center's basement parking garage. The cyanide was either consumed or so widely scattered by the huge blast that its effects were not noticed at the time of the attack. The presence of the cyanide was only uncovered after investigators found a list of the chemicals ordered by conspirator Nidal Ayyad and debriefed Basit after his arrest.

In his testimony at his 2001 trial for the Millennium Bomb plot, Ahmed Ressam described training he had received at al Qaeda's Deronta facility in Afghanistan for building a hydrogen cyanide device. Ressam said members of the group had practiced their skills, using the gas to kill a dog that was confined in a small box.

Videos found by U.S. troops after the invasion of Afghanistan supported Ressam's testimony -- as did confiscated al Qaeda training manuals that contained recipes for biological toxins and chemical agents, including hydrogen cyanide gas. The documents recovered in Afghanistan prompted the CIA to publish a report on al Qaeda's chemical and biological weapons program that created a lot of chatter in late 2004.

There have been other examples as well. In February 2002, Italian authorities arrested several Moroccan men who were found with about 4 kilograms (9 pounds) of potassium ferrocyanide and allegedly were planning to attack the U.S. Embassy in Rome.

In 2007, jihadist militants deployed a series of large vehicle-borne improvised explosive devices augmented with chlorine gas against targets in Iraq. However, the explosives in these attacks inflicted far more casualties than the gas. This caused the militants to deem the addition of chlorine to the devices as not worth the effort, and the Iraqi jihadists abandoned their chemical warfare experiment in favor of employing vehicle-borne improvised explosive devices without a chemical kicker.

There have also been several credible reports in Iraq of militants using chemical artillery rounds in improvised explosive device attacks against coalition forces, but those attacks also appear to have been largely ineffective.

Difficult to Employ

Using chemical munitions on the battlefield presents a number of challenges. The first of these is sufficiently concentrating the chemical agent to affect the targeted troops. In order to achieve heavy concentrations of the agent, chemical weapon attacks were usually delivered by a massive artillery bombardment using chemical weapons shells. Soviet military chemical weapons doctrine relied heavily on weapons systems such as batteries of BM-21 multiple rocket launchers, which can be used to deliver a massive amount of ordnance to a targeted area. Additionally, it is very difficult to control the gas cloud created by the massive barrage. There were instances in World War I and in the Iran-Iraq War in which troops were affected by chemical weapon clouds that had been created by their own artillery but had blown back upon them.

Delivering a lethal dose is also a problem in employing chemical weapons in terrorist attacks, as seen by the attacks outlined above. For example, in the March 20, 1995, attack on the Tokyo subway system, Aum Shinrikyo members punctured 11 plastic bags filled with sarin on five different subway trains. Despite the typically very heavy crowds on the trains and in the Tokyo subway stations that morning, the attacks resulted in only 12 deaths -- although thousands of other commuters were sickened by the attack, some severely.

The Syrian regime is thought to have mustard gas as well as tabun, sarin and VX nerve agents in its chemical weapons inventory. Mustard gas, a blistering agent, is the least dangerous of these compounds. In World War I, less than 5 percent of the troops who were exposed to mustard gas died. Tabun and sarin tend to be deployed in a volatile liquid form that evaporates to form a gas. Once in gas form, these agents tend to dissipate somewhat quickly. VX, on the other hand, a viscous nerve agent, was developed to persist in an area after it is delivered in order to prevent an enemy force from massing in or passing through that area. While VX is more persistent, it is more difficult to cause a mass casualty attack with it since droplets of the liquid agent must come into contact with the victim, unlike other agents that evaporate to form a large cloud.

But there are other difficulties besides delivering a lethal dose. Because of improvements in security measures and intelligence programs since 9/11, it has proved very difficult for jihadists to conduct attacks in the West, even when their attack plans have included using locally manufactured explosives. There have been numerous cases in which plots have either failed, like the May 2010 Times Square attack involving Faisal Shahzad, or been detected and thwarted, like the September 2009 plot to attack the New York subway system involving Najibullah Zazi.

Because of the improved security, it would be very difficult for jihadists to smuggle chemical agents into the United States or Europe, even if they were able to obtain them. Indeed, as mentioned above, the chemical artillery rounds used in improvised explosive devices in Iraq were employed in that country, not smuggled out of the region.

This means that jihadists not only face the tactical problem of effectively employing the agent in an attack but also the logistical problem of transporting it to the West. This difficulty of transport will increase further as awareness of the threat increases. One way around the logistical problem would be to use the agent against a soft target in the region. Such targets could include hotels, tourist sites, airport arrival lounges or even Western airliners departing from airports with less than optimal security.

Another option for jihadists or Palestinian militants could be to attempt to smuggle the chemical agent into Israel for use in an attack. However, in recent years, increased security measures following past suicide bombing attacks in Israel have caused problems for militant groups smuggling weapons into Israel. The same problems would apply to chemical agents -- especially since border security has already been stepped up again due to the increased flow of weapons from Libya to Gaza.

Militants could attempt to solve this logistical challenge by launching a warhead or a barrage of warheads into Israel using rockets, but such militant rocket fire tends to be very inaccurate and, like conventional rocket warheads, these chemical warheads would be unlikely to hit any target of value. Even if a rocket landed in a populated area, it would be unlikely to produce many casualties due to the problem of creating a lethal concentration of the agent -- although it would certainly cause a mass panic.

The use of chemical weapons would also undoubtedly spur Israel to retaliate heavily in order to deter additional attacks. This threat of massive retaliation has kept Syria from using chemical weapons against Israel or allowing its militant proxies to use them.

Hezbollah may be the militant organization in the region that could most effectively utilize Syrian chemical munitions. The group possesses a large inventory of artillery rockets, which could be used to deliver the type of barrage attack required for a successful chemical weapon attack. Rumors have been swirling around the region for many months that Libyan rebels sold some chemical munitions to Hezbollah and Hamas. While we have seen confirmed reports that man-portable air-defense systems and other Libyan weapons are being smuggled into Sinai en route to Gaza, there has been no confirmation that chemical rounds are being smuggled out of Libya.

Still, even if Hezbollah were to receive a stockpile of chemical munitions from Syria or Libya, it has a great deal to lose by employing such munitions. First, it would have to face the aforementioned massive retaliation from Israel. While Israel was somewhat constrained in its attacks on Hezbollah's leadership and infrastructure in the August 2006 war, it is unlikely to be nearly as constrained in responding to a chemical weapon attack on its armed forces or a population center. Because of the way chemical weapons are viewed, the Israelis would be seen internationally as having just cause for massive retaliation. Second, Hezbollah would face severe international repercussions over any such attack. As an organization, Hezbollah has been working for many years to establish itself as a legitimate political party in Lebanon and avoid being labeled as a terrorist organization in Europe and elsewhere. A chemical weapon attack would bring heavy international condemnation and would not be in the group's best interest at this time.

So, while securing Syrian chemical munitions is an imperative, there are tactical and practical constraints that will prevent militants from creating the type of nightmare scenario discussed in the media, even if some chemical weapons fell into the wrong hands.